The present invention relates to partially adaptive arrays. More specifically, the present invention relates to partially adaptive arrays of greater than 1000 elements that use a bootlace lens.
A fully adaptive array is one in which every element of the array is individually controlled adaptively. An adaptive array is one of the best available means to reject unwanted noise and interferences and is ideal for the purpose of removing jamming. However, in practice, due to the complexity of the adaptive network, most adaptive arrays are limited to only a few elements. The ever increasing requirement of high gain and high resolution leads to large arrays with thousands of elements. To develop a fully adaptive array for such a system is neither economical nor technically feasible.
A partially adaptive array is one in which elements are controlled in groups (the subarray approach) or in which only certain elements called auxiliary elements are made controllable. A partially adapted array greatly reduces the number of adaptive processors and its complexity and hence its cost. However, performance of such a system is limited and as the number of elements increases the complexity of the system once again poses a problem.
A butler matrix has been proposed to process all the elements of a fully adaptive array. See S. P. Applebaum, P. J. Chapman, "Adaptive Arrays with Main Beam Constraints," IEEE Trans. on ANT and Prop., Vol. AP-24, No. 5, Sept 1976. However, the butler matrix may have the same problems of complexity as mentioned above if one attempts to adapt with a large number of beams (more than 1000).